Journal of Insect Science: Vol. 13 | Article 24 Omkar and Kumar Responses of an aphidophagous ladybird beetle, Anegleis car- doni, to varying densities of Aphis gossypii Downloaded from https://academic.oup.com/jinsectscience/article/13/1/24/1068211 by guest on 23 September 2021 Omkara* and Gyanendra Kumarb Ladybird Research Laboratory, Department of Zoology, University of Lucknow, Lucknow-226007 (India) Abstract Laboratory experiments were conducted to determine the functional and numerical responses of fourth instar larvae, adult male, and adult female ladybird beetles, Anegleis cardoni Weise (Cole- optera: Coccinellidae), to different densities of aphids, Aphis gossypii Glover (Hemiptera: Aphididae), on the bottle gourd, Lagenaria vulgaris Seringe (Cucurbitales: Cucurbitaceae). The results revealed a density dependent, Type II functional response of A. cardoni. Prey consump- tion increased curvilinearly with an increase in prey density for all three predatory stages. Numerical responses revealed significant increases in oviposition with increases in prey density. The food exploitation efficiency and the efficiency of conversion of ingested food decreased with increases in prey density. The attack rate was highest for adult females, followed by fourth instar larvae and adult males. Prey consumption was highest and handling time lowest in fourth instar larvae, followed by adult females and males. Therefore, fourth instar larvae of A. cardoni may be considered the most efficient predatory stage in aphid management strategies. Keywords: ECI, food exploitation, functional response, numerical response. Abbreviations: ETC, environmental test chamber Correspondence: a [email protected], b [email protected] *Corresponding author Editor: TX Liu was editor of this paper. Received: 11 August 2011 Accepted: 17 July 2012 Copyright : This is an open access paper. We use the Creative Commons Attribution 3.0 license that permits unre- stricted use, provided that the paper is properly attributed. ISSN: 1536-2442 | Vol. 13, Number 24 Cite this paper as: Omkar, Kumar G. 2013. Responses of an aphidophagous ladybird beetle, Anegleis cardoni, to varying densities of Aphis gossypii. Journal of Insect Science 13:24. Available online: http://www.insectscience.org/13.24 Journal of Insect Science | http://www.insectscience.org 1 Journal of Insect Science: Vol. 13 | Article 24 Omkar and Kumar Introduction Coccinellids, commonly known as ladybird beetles, form an important group of biocontrol agents among insect predators due to their ability to feed on a variety of prey, e.g., aphids, mealy bugs, scale insects, whiteflies, thrips, and many more (Dixon 2000; Omkar and Pervez 2004). The effectiveness of preda- Downloaded from https://academic.oup.com/jinsectscience/article/13/1/24/1068211 by guest on 23 September 2021 tors depends upon their interactions with different prey species. To describe the nature of predation, Solomon (1949) proposed func- tional and numerical responses. Functional and numerical responses are used to assess the impact of a predator on the population dynam- ics of its prey (Murdoch and Briggs 1996). Functional response has been categorized into Figure 1. Life cycle of Anegleis cardoni. High quality figures are Type I, Type II, and Type III (Holling 1959), available online. Type IV (i.e., dome shaped; Luck 1985; Bres- sendorff and Toft 2011) and Type V (i.e., tor. This increase in predators may be because negative exponential; Watt 1959; Sabelis the predators aggregate in areas of high prey 1992). Most studies reveal Holling’s Type II density, or because the reproduction and sur- functional response in coccinellids (e.g., Dix- vival rate of predators increases. The on 2000; Lee and Kang 2004; Pervez and aggregation of predators in response to chang- Omkar 2005; Moura et al. 2006; Omkar and ing prey resources may lead to higher attack Pervez 2011), with only a few reporting Type rates by the predator. In nature, predators are III responses (e.g., Messina and Hanks 1998; known to respond both functionally and nu- Sarmento et al. 2007). merically towards their prey population, but functional response is known to be the key Disturbances while searching for prey and factor, as it is thought to be the determinant of feeding can result in interference or stimula- numerical response (Keith et al. 1977). There- tion. The number of prey killed increases with fore, the functional and numerical responses increases in prey density due to the interfer- of a predator towards the changing density of ence-stimulation factor (Sandness and a prey population are characteristics to evalu- McMurtry 1970). All these factors may affect ate the suitability of the predator. a predator’s attack rate (a) and handling time (Th), which are the key factors of functional Anegleis cardoni (Weise) (Coleoptera: Coc- response. Evaluation of these two parameters cinellidae) (Figure 1) is a medium-sized is important when assessing the type of func- ladybird beetle, and is known to feed on a va- tional response. In addition to attack rate and riety of aphids, e.g., Brevicoryne brassicae L. handling time, the number of predators can (Hemiptera: Aphididae), Macrosiphum mis- also change as the number of prey increases, canthi (Takahashi), Macrosiphum pisi which is the numerical response of the preda- Kaltenbach (Afroze 2000), as well as Aphis Journal of Insect Science | http://www.insectscience.org 2 Journal of Insect Science: Vol. 13 | Article 24 Omkar and Kumar gossypii Glover, Aphis craccivora Koch, and Lipaphis erysimi Kaltenbach (Omkar et al. 2009) and many other aphids (Omkar et al. 2011). Futhermore, it has also been reported to prey on whiteflies (Ramani et al. 2002) and scale insects (Sundararaj 2008). Although previous studies have focused on the influence of prey quality and quantity on A. cardoni (Afroze 2000; Omkar et al. 2009; Omkar et al. 2010; Omkar et. al. 2011), there is no infor- Downloaded from https://academic.oup.com/jinsectscience/article/13/1/24/1068211 by guest on 23 September 2021 mation on prey-predator population dynamics, which is important in evaluating the perform- ance of A. cardoni to a changing prey density and forecasting the suitability of the predator Figure 2 Experimental setup for functional response of fourth as a potential biocontrol agent. Therefore, this instar larvae of Anegleis cardoni. A: 320 third instar Aphis gossypii, study was designed to investigate the func- one fourth instar A. cardoni, and a piece of Lagenaria vulgaris leaf per beaker (photo in zoom shows arena in a single beaker). B: tional and numerical responses of A. cardoni beakers covered with muslin cloth and fastened with a rubber on its preferred aphid prey, A. gossypii under band. C: environmental test chamber. High quality figures are laboratory conditions. available online. A. gossypii until adult emergence. The aphid supply was refreshed every 24 hr. Newly Materials and Methods emerged adults were reared in Petri dishes (same size as above) on the same aphid-host Stock Maintenance plant complex. Adults of A. cardoni collected from trees of False Ashoka, Polyalthia longifolia (Magno- Experimental Protocol liales: Annonaceae), were grouped in Petri Functional response. Different predatory dishes to identify mating pairs. Thereafter, stages of A. cardoni, i.e., fourth instar larvae mating pairs were transferred to other Petri and 15-day-old, unmated, adult males and fe- dishes (9.0 x 1.5 cm) and kept under con- males were taken from stock culture and trolled abiotic conditions (27 ± 2º C, 65 ± 5% starved for 12 hr in the ETC under the previ- RH, and 14:10 L:D photoperiod) in an envi- ously mentioned abiotic conditions. ronmental test chamber (ETC). Pairs were Thereafter, they were kept separately in beak- provided ad libitum with A. gossypii infested ers (9.5 × 6.5 cm) and provided with variable on the bottle gourd, Lagenaria vulgaris Ser- numbers of third instar A. gossypii together inge (Cucurbitales: Cucurbitaceae), together with host plant leaves (Figure 2). Beakers with host plant leaves collected from field. were covered with muslin, fastened with a Egg laying and hatching were recorded twice rubber band, and kept in the ETC. After 24 hr, a day. Precautions were taken so that larvae predators were removed from beakers, and the did not consume their egg chorions after number of unconsumed aphids was counted. hatching. Larvae were shifted into 250 mL, The experiment was replicated ten times for open-topped, cylindrical, glass beakers (9.5 × each predaceous stage at different prey densi- 6.5 cm) and kept in the ETC. Each beaker ties, i.e., 10, 20, 40, 80, 160, and 320. Aphid contained five larvae. Larvae were reared on Journal of Insect Science | http://www.insectscience.org 3 Journal of Insect Science: Vol. 13 | Article 24 Omkar and Kumar supply was not replaced during the experi- dence intervals (Juliano 2001). Type III ment. functional response follows the equation: Data Analysis Ne = No {1- ex [(d + b No) (Th Ne - T) / (1+ Functional response analysis involves deter- c No)]} (3) mination of the type of functional response and estimation of the parameters of functional where b, c, and d are constants. response curves (Juliano 2001). To distinguish between Type II and Type III responses, the Data obtained from prey consumption by shape of the functional response curve was fourth instar larvae and adult females and Downloaded from https://academic.oup.com/jinsectscience/article/13/1/24/1068211 by guest on 23 September 2021 analyzed with the help of a logistic regression males at different prey densities were sub- (Juliano 2001) of the proportion of prey eaten jected to one-way ANOVA, and means were (Ne) as a function of initial prey density (No). compared using Tukey’s honestly significant The data were fitted to a polynomial function difference test at 5% levels using statistical using statistical software SAS (Version 9.0, software MINITAB- 2003 http://www.sas.com/). The equation used was: (http://www.minitab.com/) on a personal computer (PC).